Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are provided, and the description does not disclose side effects, read-only behavior, error handling, or whether it accesses any external resource. Saying 'Values discarded' hints at non-mutating behavior, but it is insufficient for an agent to predict side effects confidently.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is extremely concise and front-loaded, with no filler or redundant wording. It communicates the core action in two short sentences.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Key context is missing: whether top-level keys only or all nested keys are counted, whether the input is a JSON object or JSON string, and what the return value looks like. The absence of an output schema compounds this ambiguity.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Although the schema has 100% description coverage, many parameter descriptions appear unrelated to counting JSON keys (e.g., ref, url, city, zone). The description does not clarify which of the nine optional strings is the JSON object, and the 'json' field is described as 'JSON text to validate' rather than as the object whose keys are counted.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a clear action ('Count keys') and a resource ('JSON object'), but it does not specify which schema parameter holds the JSON object or what the output is. The tool name and description are understandable in isolation, yet the mismatch with the input schema creates ambiguity.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

No guidance is provided for when to use this tool instead of related siblings such as validate-json or search-query-len. It does not mention prerequisites, expected input shape, or typical use cases.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.